1. Field of the Invention
Aspects of the present invention relate to a cathode and a lithium battery including the same, and more particularly, to a cathode having a high capacity and conductivity and a lithium battery including the same.
2. Description of the Related Art
Generally, an oxide such as LiNiO2, LiCoO2, LiMn2O4, LiFePO4, LiNixCo1-xO2(x=1, 2), and LiNi1-x-yCoxMnyO2 (0≦x≦0.5, 0≦y≦0.5) been used as a cathode active material for lithium batteries.
A high capacity lithium battery can be developed by improving the efficiency and capacity of the cathode active material. A high capacity lithium battery is desirable for complex and highly functional portable electronic devices. Accordingly, it is desirable to develop better materials for lithium batteries.
For example, a variety of materials having high capacity such as composite oxides are used as cathode active materials. Among the composite oxides, for example, there is xLi2MO3/(1−x)LiMeO2, which basically includes Li2MO3 and LiMeO2. However, some composite oxides have disadvantages. In Li2MnO3, for example, the initial oxidation state of Mn is +4, and the oxidation-reduction potential of Mn4+/5+ is below the balance band and thus Mn cannot contribute to improving the electrical conductivity. In addition, in a solid solution composition that may be used in practice, the amount of lithium is about 10-20% of the transition metal layer due to overlithiation, and the amount of Mn is at least twice as much as the amount of lithium. Thus, a only a small amount of the transition metal is used in electrical conductivity, thereby decreasing electrical conductivity.
Thus, it is desirable to improve the conductivity of various cathode active materials including such a composite oxide. Attempts have been made to improve the conductivity of the cathode active material by increasing the efficiency of the cathode active material by mixing the cathode active material with a material having excellent conductivity, and by employing a material having excellent conductivity as a conducting agent included in the cathode. However, there is still a need to develop a high capacity lithium battery.